1. Field of the Invention
The present invention generally relates to bus controllers and, more particularly, to a bus controller for controlling connection of bus agents to a bus.
Recently, as the operating speed of computer systems is improved, a demand for a high-speed bus inside a system is growing. In order to facilitate improvement in the speed of a bus, the standards impose a severe requirement for electrical performance on a bus. In order to insure a stable operation in the bus constructed under the severe requirement, the electrical characteristic of the bus should be stabilized.
2. Description of the Related Art
Conventionally, a bus is provided with a plurality of connectors so that a bus agent in the form of an add-in card is connected to each of the connectors. The number of bus agents connected to the bus is variable. No bus controller for managing the bus agents connected to the bus is provided. Each of the bus agents connected to the bus continually decodes an address delivered on the bus so as to determine whether an access to the bus agent occurs.
The load imposed on a driver (also provided in each of the bus agents) for driving the bus varies depending on the number of bus agents connected to the bus. For this reason, the operation of the bus with a severe requirement for electrical performance may be unstable.
Since the bus agents are operated such that even those bus agents connected to the bus but not accessed for a long period of time decode an address delivered on the bus, there is a problem in that an unnecessarily large power consumption may result.